Shovel



Och 6 1925- F. C. BRANDENBURG SHOVEL Filed Jan. 17, 1921 TTOR Patented Oct. 6, 1925. l

UNITED-f STATES 1,556,200 PATENT. oFFicE.

FRANCIS c. BRANDENBURG, oF PIQUA, oHIo, AssrcNoR'To THE woon sHovEL AND i,

rrooI. COMPANY, or PIQUA, omo', A CORPORATION or"y 0R10.

sHovEL. l'

` Application 1ed yJanuary 17,1921, Serial No. 437,763.`

ful Improvementr in Shovels, of whichthe following is a specification.

My invention relates t0 shovels, as articles of manufacture, in which the cutting edge,

i. e., the edge that must cut or slide under the material to be lifted by the shovel, is stiffened and held straight by a slight bend or camberl a short distance from and parallel to the cutting edge; and in which the shovel is hardened by heat-treatment. In the accompanying drawing, Figure l is a perspective view of a shovel embodying my present invention and Figure 2 is a longitudinal sectional view thereof.

Outward'ly this shovel resembles many others, but it differs from them in that the structure of the metal composing it contributes to the maintenance of a predetermined form, where in other shovels, especially heat-treated shovels, the desired form, if it is maintained at all, is maintained by a sort of balance or equilibrium` of opposing strains, each tending to distort the metal.

Heat-treating shovels is not new; neither is it new to provide heat-treated shovels with the camber. But certain difliculties have been encountered by those who produce heat-treated cambered shovels, the principal of which is that such shovels do not retain their shape. Sooner or later they become distorted. It is not practicable, obviously, to bend the shovel after it is heat-treated. Even if the metal s not too hard to permit of its being bent, bending it after it has been heat-treated sets up internal and opposing stresses in the metal, which either immediately or eventually distort the shovel, so that the edge becomes crooked and its usefulness much impaired. Neither is it practicable to make the bend before the heat-treating is done, because of the tendency of the metal to warp and become distorted during the heat-treatment. This has been tried, and is being done by others, and it is to overcome the difficulties encountered by those who use.l

that method that I have devised my new method. As is well known, there is always more or less certainty that sheet metal will warp during heat-treatment, and in a case such as forming the camber in a shovel, this the crystalline structure is inert;

condition is much aggravated. The eXcessive tendencyofthe camber to warp during heat-treatment is due to the slightness of they bend in the metal. Where a considerableV orvvery sharp bend is made in sheet metal, a certain Vdisruption of the bonds unit-ing the metallic crystals occurs, which eliminatesfto a considerable extent, if not wholly, the 'tendency for 4the metal to return to its former shape. In other words, the metal is strained beyond its elastic limit and becomes set in .its new position. In cambering a shovel the metal is bent so slightly that it is not strained to its elastic Y limit, or at least not to the extent necessary to eliminate all tendency to return to .its former shape, and the shovel `is certain to warp when the metal is heated. At present this diiiculty is being met byother shovel makers by straightening the shovels with a hammer after they are heat-treated.

To overcome the diliiculties described I have developed a method kfor simultaneously cambering and heat-treating shovels. Briefly, this method consists in providing a pair of forming dies between which the lower end of a heated shovel may be clamped and the desired camber formed therein. This device is immersed in a quenching liquid and means provided for operating the dies while immersed. The shovel is heated to a degree above the critical temperature of the metal, then plunged into the quenching liquid and clamped between the dies before the metal has had time to cool below its critical temperature. The metal is very malleable when heated above its critical temperature, and its crystals, also the blonds unting them, readily adapt themselves to their new positions, so that when the metal is cooled the structural arrangement of the metal, that is, the crys talline formationv of the metal is such as tends to maintain the position it was forced by the dies to assume. It may be said that i. e., the bonds uniting the crystals tend to hold the crystals in the position they occupied while the shovel was between the dies, and the metal is therefore devoid of tendency to assume another form. The metal not only has no tendency to change its shape, but 1t is endowed with power to resist extraneous strains tending to distort it.

My shovels are thus distinguished in a very important and deiinite Way from those which are allowed to Warp during heattreatment and afterward straightened With a hammer or by other' means. rlhey are unWarped, not de'vvarped. Straightening the hardened metal after it has warped simply sets up opposing strains Which, though tor the time being may balance one another and hold the metal straight, eventually become unbalanced and distortion oi the metal follows. If this does not occur through the ordinary seasoning process which the metal undergoes, it is brought about by strains occurring in the ordinary use of the shovel, or because of the wearing away of parts of the metal which constitute elements in the artificially created equilibrium of strains. In my shovel the metal is given its form While hot, the constituents of the metal being then in a state of repose, and the metal is hardened With the saine heat. Therefore, the crystalline structure is in harmony with the torni of the shovel. The metal is not only tree from strains tending to distort it, but being inert its entire mechanical strength is available for resistence to external strains tending to distort it. Moreover, since the constituents of the metal are in a state of repose, my shovels retain their shape as they wear out.

In addition to the obvious advantage of lkeeping the cutting edge straight, so that When the shovel is used, say to lift ashes or coal, it bears on the ground or floor over the entire Width of the shovel, the camber is also advantageous in that it insures a narrow contact with the floor, which contact is certain to be at the cutting edge.

In an application filed concurrently with the present one, Serial No. 437,764 I have described my method in detail and also apparatus for putting the method into effect. So it is deemed unnecessary to repeat the description here.

Having fully described my new article of manufacture, what I claim is as Jollovvs:

l. A heat-treated steel shovel having a straight cutting edge, the heat-treated metal in said shovel being substantially free from stresses produced by cold Working.

2. A heat-treated steel shovel having a straight cutting edge and a camber near and parallel to said edge, the heat-treated metal composing the shovel being substantially tree troni stresses produced by cold Working.

3. A heat-treated steel shovel having a straight, single ply, cutting edge, the heattreated metal in said shovel being substantially free from stresses produced by cold Working.

4. heat-treatnient-hardened steel shovel having a straight cutting edge, the hardened metal in said shovel being substantially free from stresses produced by cold Working.

FRANCIQ C. BRANDENBURG. 

